Star Formation Efficiencies at Giant Molecular Cloud Scales in the Molecular Disk of the Elliptical Galaxy NGC 5128 (Centaurus A)
Journal article, 2019
We present ALMA CO (1-0) observations toward the dust lane of the nearest elliptical and radio galaxy, NGC 5128 (Centaurus A), with high angular resolution (similar to 1 '', or 18 pc), including information from large to small spatial scales and total flux. We find a total molecular gas mass of 1.6 x 10(9) M-circle dot and reveal the presence of filamentary components more extended than previously seen, up to a radius of 4 kpc. We find that the global star formation rate is similar to 1 M-circle dot yr(-1), which yields a star formation efficiency (SFE) of 0.6 Gyr(-1) (depletion time tau = 1.5 Gyr), similar to those in disk galaxies. We show the most detailed view to date (40 pc resolution) of the relation between molecular gas and star formation within the stellar component of an elliptical galaxy, from a scale of several kiloparsecs to the circumnuclear region close to the powerful radio jet. Although on average the SFEs are similar to those of spiral galaxies, the circumnuclear disk (CND) presents SFEs of 0.3 Gyr(-1), lower by a factor of 4 than the outer disk. The low SFE in the CND is in contrast to the high SFEs found in the literature for the circumnuclear regions of some nearby disk galaxies with nuclear activity, probably as a result of larger shear motions and longer active galactic nucleus feedback. The higher SFEs in the outer disk suggest that only central molecular gas or filaments with sufficient density and strong shear motions will remain in similar to 1 Gyr, which will later result in the compact molecular distributions and low SFEs usually seen in other giant ellipticals with cold gas.
galaxies: star formation
ISM: molecules
galaxies: individual (NGC 5128)
galaxies: nuclei
galaxies: elliptical and lenticular, cD
Author
D. Espada
The Graduate University for Advanced Studies (SOKENDAI)
National Astronomical Observatory of Japan
S. Verley
Universidad de Granada
R. E. Miura
National Astronomical Observatory of Japan
F. P. Israel
Leiden University
C. Henkel
King Abdulaziz University
Max Planck Society
S. Matsushita
Academia Sinica
B. Vila-Vilaro
European Southern Observatory Santiago
Atacama Large Millimeter-submillimeter Array (ALMA)
J. Ott
National Radio Astronomy Observatory Socorro
K. Morokuma-Matsui
Japan Aerospace Exploration Agency (JAXA)
University of Tokyo
A. B. Peck
Gemini Observatory North
A. Hirota
Atacama Large Millimeter-submillimeter Array (ALMA)
National Astronomical Observatory of Japan
Susanne Aalto
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics
A. C. Quillen
University of Rochester
M. R. Hogerheijde
University of Amsterdam
Leiden University
N. Neumayer
Max Planck Society
C. Vlahakis
National Radio Astronomy Observatory
D. Iono
The Graduate University for Advanced Studies (SOKENDAI)
National Astronomical Observatory of Japan
K. Kohno
University of Tokyo
Astrophysical Journal
0004-637X (ISSN) 1538-4357 (eISSN)
Vol. 887 1 88Subject Categories
Astronomy, Astrophysics and Cosmology
Other Earth and Related Environmental Sciences
Geosciences, Multidisciplinary
Infrastructure
Onsala Space Observatory
DOI
10.3847/1538-4357/ab262d